A variety of electrical loads, such as ECUs (Electronic Control Units), various sensors, lamps, and motors, are mounted in a vehicle. Power is supplied to these electrical loads from a power supply such as a battery. In a vehicle, whether or not to supply power to the respective electrical loads needs to be switched in accordance with the state of an ignition switch or an accessory switch. For this reason, electromagnetic relays are provided in power supply paths from the power supply to the electrical loads, and the power supply to the electrical loads is individually controlled by individually controlling whether to set the electromagnetic relay to a conductive state or a cut-off state.
The invention described in JP 2009-289671A is a relay control device that causes a large current to flow through a relay coil when a relay circuit starts to be driven, and causes a small current to flow through the relay coil after a relay contact has turned on. This relay control device reduces the current flowing through the relay coil after the relay contact has turned on to reduce the heat generated by the relay coil.
In a configuration in which the power supply to an electrical load is controlled by an electromagnetic relay, the coil needs to be energized so as to set the electromagnetic relay to a conductive state. Due to causing a large current to flow through the coil, there is a concern about the heat generated by the coil, the life of the coil being adversely affected, or the like.
The invention has been made in view of the foregoing situation, and aims to provide a relay control device capable of reducing the amount of power supplied to a coil in an electromagnetic relay.